1. Field of the Invention
The present invention relates to a photomask material for use in manufacture of a semiconductor device.
1. Description of the Prior Art
FIG. 1 is a diagram of a conventional photomask material which has been used in manufacturing a semiconductor device. The conventional photomask material comprises a transparent glass substrate 1, such as silica, and a metal layer 2, such as chromium, which is formed with a thickness of about 1000.ANG. by means of an evaporation process, sputtering and the like.
A mask used for manufacturing a semiconductor device included a photography emulsion dry plate using a transparent glass substrate. However, with the advance of high integration and fining, a hard mask including a transparent glass substrate and a metal film such as chromium formed on the glass substrate has been widely used. The metal film such as chromium is generally formed by mean of an evaporation, sputtering process and the like so that the thickness thereof is about 600-800.ANG..
A photomask for semiconductor device is made by first applying photoresist or resist for an electron beam (EB) on to the metal film and then drawing patterns by light or electron beam, followed by the process such as development and etching.
In a case where a metal film is made of chromium, a wet etching process is generally used, in which ammonium cerium (IV) nitrate and perchloric acid are employed. On the other hand, if and when a dry etching process in case of a metal film of chromium includes the use of a mixed gas of carbon tetrachloride (CCl.sub.4) and oxygen (O.sub.2). In manufacturing a mask for semiconductor device, particularly having fine patterns with high integration, such as VLSI, a dry etching process having less side etch effect is preferred.
The use of a general wet etching process in manufacturing a chromium mask for a semiconductor device makes it difficult to manufacture a mask with high accuracy, because of side etching effect or the like. On the other hand, according to a dry etching process which is advantageous for a mask with high accuracy, the etching speed of chromium is less than 100.ANG./min and selection ratio to resist (the etching speed of chromium to etching speed of resist) is worse, which is not suitable for mass production. In addition, in case of chromium mask, joining ability between the chromium film and the silica glass substrate is so small that fine pattern is sometimes stripped off when washed.
Incidentally, Japanese Patent Application No. 42176/1981, filed Mar. 23, 1981 and laid open for public inspection Sept. 28, 1982 and Japanese Patent Application No. 42183/1981, filed Mar. 23, 1981 and laid open for public inspection Sept. 28, 1982 discloses that a silicon layer and a metal layer are deposited on a glass substrate so that a pattern of silicide is formed by an electron beam.